There is a lot you can't do with iWeb, but there is also a lot you can do, it is a matter of creativity or excess of free time. Templates are customizable enough for most basic tasks, like changing or creating the background, changing colors or fonts, changing the layout... if you can be a little more specific i may be ableto help you step by step.
About the guestbook, there is only one true iWeb-based option, you can create a blog entry and use it's comment section as a guestbook, just be sure to link to it only. You can use some external guestbooks but those requiere a little bit of editing in the created/published page, try HaloScan, it is free and requires minimal changes.
About your having your name as part of your address, the only solution i can think of is using a web-host service, a frame-based page there and use you .Mac account to store the site, like the author of What The Duck.